The magnetic core of an electrical transformer can be formed of a number of laminated thin strips of a material which can be readily magnetized. The core material, for example, can be silicon steel or Metglas (TM). To make the core, the magnetic strips are formed into a loop. This loop is in the form of a circular shape, and, if desired, thereafter it is formed into a rectangular shape. The joints of each lamination in the core are positioned in a prescribed attitude to enhance the magnetic qualities of the loop. After formation the core is annealed. It can then be assembled with a coil as a final step.
Metglas (TM) is an amorphous, crystalline material which is very brittle. Thus, the laminations in such a core need protection. If they are not properly protected and they are bumped, dropped or otherwise improperly contacted, they can shatter or deform. In either case, the transformer may not function properly as a result of the contact.
Thus, there is a need to retain the core laminations, and to surround and protect the laminations from bumping, dropping, or other contact. This can be accomplished with a retainer which protects the core through formation, annealing, and also after the core is assembled with a coil.
Several methods of retaining metallic transformer cores have been suggested in the prior art. In U.S. Pat. No. 4,673,907, a band which is tightened and then clipped at its free ends to hold it in place is used to hold clamping plates and insulating plates in place, which in turn retain a metallic core. U.S. Pat. No. 4,723,349 discloses interlocking joints 116, 118 which hold two U-shaped members in place, and which in turn retain a metallic core. Each interlocking joint uses a tongue-in-slot arrangement. U.S. Pat. No. 4,364,020 discloses a protective outer layer for a core assembly made of silicon steel to protect the core. In U.S. Pat. No. 4,663,605, flexible banding under tension clamps two plates spaced outwardly from two yokes, and the clamping forces are transmitted to the coil structures by paths which bypass a rectangular core. The band is preferably held in place by a clip 68.
A retaining system which is simple, inexpensive, and easy to use is described below.